Economy thermal imager?

Fester Bestertester wrote in news: snipped-for-privacy@news.eternal-september.org:

Probably not. While it's common practise to remove an IR filter to image what a near-IR laser or other diode is doing, it wouldn't work for long-wave IR like a CO2 laser and the emissions from something hot, unless it was almost hot enough to be visible anyway. But try it, you might get enough milage out of it. it will be cheaper to try it that to find out what you need if it doesn't work so you have to try it, no?

A *much* broader spectrum out to long wave IR and also a silicon lens. Glass does not transmit the wavelengths needed for thermal imaging. There is a good reason why they are so expensive.

You can do near IR with a modified digicam and a low pass filter - enough to make diagnosis of foliage diseases in trees perhaps but nothing like enough to see temperature differences unless the target was almost at red heat. I doubt if a soldering iron would show up at all on a normal digicam CCD in the IR.

You can buy relatively cheap non contact IR thermometers and use a servo to scan one to build up a low resolution thermal image.

Regards, Martin Brown

No. Silicon doesn't go very far into the IR, ditto all the glass optics. for thermal imaging you're looking at about an order of magnitude longer wavelength, whearas silicon devices would struggle to image double the wavelength of the deepest visible red.

thermal imaging you're

devices would struggle to

These lenses are made of germanium, very expensive!!

More likely, you need to PLACE an IR filter in front of a camera image chip, and boost its gain.

If you know where your hot spots develop, you can mount properly pointed, dedicated IR sensors without the need for imagery.

Melexis makes non-expensive IR thermometers:

Those are the transducers themselves. Not much good on their own. All appear to sport a Germanium window, though the first one has a small cartoon superimposed over it.

Harbor freight sells nice IR thermometer units. You can get the fresnel jobs and point at the target from the right distance, and remove the need to "scan" a rudimentary image. like some have described. It would sense the change anywhere in its field of view.

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The Sony Exview B&W CCD have response beyond a micron. Since a digital camera or camcorder will have a RGB matrix, only a fraction of the pixels will have IR response, so the low resolution of NTSC camera isn't all that crappy since at least all the pixels will have some response.

You can see a soldering iron in the dark with one of these exview CCDs, but this is only because the iron is stinkin hot and the black body radiation has a long exponential tail. That is, you don't see the peak of the thermal image. Averaging the image helps since you are dealing with a noisy signal.

Don't set your expectations too high as far as thermal sensing goes. Otherwise, these low light cameras are pretty cool, certainly on par with gen 1 NV.

Might as well buy the real IR imagers that the security camera folks are pushing now, if you are going to do that.

I think they sell them by the box at Frys'.

That isn't the same thing. This all gets really confusing unless you sit back and look at what all these objects (NV, IR, thermal) do. NV is light amplification. It has a bit of IR sensitivity, so low grade NV uses IR illuminators. Thermal imaging is in the 10um range, It really detects infrared. Cameras like what Fry;s is selling are just CCDs with IR illuminators. Real NV just amplifies star light.

The deal is IR illuminators don't go very far, so if you depend on IR illumination, you can't see very far and you are a serious target for anyone else with a CCD, NV, or thermal. Your life expectancy in war time would be that of a Marine flame thrower.

The original poster is trying to detect IR, so painting with IR won't do the trick. There is also the Phil Hobbs $10 detector he posts when this subject comes up. It's a good paper, though I don't know about the price.

The Sony exview CCD is a very sensitive detector with just a bit of near IR response, maybe out to a 1um, but not flat.

Go to ebay, google probeye every once in a while. replace some small rubber belts inside.

Find a dive shop, they can refill the hughes argon tanks for the joule thompson cooleras they pressure test the dive tanks with HP Argon/

About as cheap as thermal imaging gets, as low as 250$ every once in a while.

room temperature thermal really does not kick in until you get to 3.5 microns and better home ones would cover 8-12 microns.

raytheon imagers show up, but I could never find one of the 240x320 cadillac deville ones, seems most of them died before the car made it to the junk yards. I'm told once in a while a car dealer finds one on the shelf and lets them go at 2400$ each

only way to make anything decent with the most of the IR motion sensors out there is to put a chopper wheel in front of them and use them for very close targets, they are not all that sensitive and will see things just out of their field of view better then they would see a far away cold room temp target. They are piezo, and thus only respond to a AC (chopped) signal, unless you can find a newer single element or 4x4 array bolometer ie melexys.

Phil Hobbs design rocks $ for $ compared to anything else other then a bolometer chip.

Or if you can find a anesthesia gas analyser of the more modern compact kind, you can find a single element sensor with a TE cooler in the package and use a pair of galvo mirrors for scanning and and a old lens from a laser cutting shop co2 laser for the objective lens. The Anesthesia Analyser are usually 3-8 microns or so, but need the cooling and a bias current and a chopper wheel, they usually have dichroic filters on a chopper wheel for optical adsorption bands for each gas. I've picked up the modules at my local surplus place for 50 cents from time to time, and mine are not for sale.

Steve Roberts

No, for a variety of reasons.

Visible light spans about an octave -- something a bit shorter than 800 nanometers to something a bit shorter than 400, IIRC.

IR midwave is 3-5 microns; that's four times longer than visible light. Glass won't transmit it so you need special lens materials, silicon diodes won't detect it so you need special detector materials, and your whole damn camera body glows so you have to design and build the optical path with great care.

IR long wave (where the inexpensive bolometer-style detectors work) is

Mikron and FLIR were the Cadillacs.

And raytheon's cheapest bolometer was the one in the deville front grill, there is a complete system from the car on ebay starting at

I agree 320 is a waste of time, but he's asking for a hobby system.

Steve

There's a reason a FLIR costs $10K.

John

Oh WOW! I thought you were actually calling a Raytheon imager product "The Cadillac" of the crop kind of thing. I totally missed that you were referring to it actually being a product installed onto a Caddy.

There are many out there, but shopping for the right price to get a good value is difficult with the online world.

Hell, even at Fry's you cannot examine a working item more than half the time. I hate that sight unseen crap!

Yeah... it is called greed, and the knowledge that most of your buyers are rich government funded factions.

The detector is pretty exotic, and the retail price of the germanium lens is a couple of $K.

FLIR recently bought Extech, and has a new, lower-price thermal imager.

John